the impact of supplemental antioxidants on visual function ......meso-zeaxanthin (mz), zeaxanthin...

Clinical Trials

The Impact of Supplemental Antioxidants on VisualFunction in Nonadvanced Age-Related MacularDegeneration: A Head-to-Head Randomized Clinical Trial

Kwadwo Owusu Akuffo,1 Stephen Beatty,1 Tunde Peto,2 Jim Stack,1 Jim Stringham,3 DavidKelly,1 Irene Leung,4 Laura Corcoran,1 and John M. Nolan1

1Macular Pigment Research Group, Nutrition Research Centre Ireland, School of Health Sciences, Waterford Institute ofTechnology, Waterford, Ireland2Centre for Public Health, Queen’s University Belfast, Belfast, United Kingdom3Nutritional Neuroscience Laboratory, Department of Physiology and Pharmacology, University of Georgia, Athens, Georgia, UnitedStates4NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London,United Kingdom

Correspondence: John M. Nolan,Macular Pigment Research Group,Nutrition Research Centre Ireland,Waterford Institute of Technology,West Campus, Carriganore, Water-ford, X91 K236, Ireland;[email protected].

KOA and SB are joint first authors.

Submitted: November 28, 2016Accepted: September 10, 2017

Citation: Akuffo KO, Beatty S, Peto T,et al. The impact of supplementalantioxidants on visual function innonadvanced age-related macular de-generation: a head-to-head random-ized clinical trial. Invest Ophthalmol

Vis Sci. 2017;58:5347–5360. DOI:10.1167/iovs.16-21192

PURPOSE. The purpose of this study was to evaluate the impact of supplemental macularcarotenoids (including versus not including meso-zeaxanthin) in combination withcoantioxidants on visual function in patients with nonadvanced age-related maculardegeneration.

METHODS. In this study, 121 participants were randomly assigned to group 1 (Age-Related EyeDisease Study 2 formulation with a low dose [25 mg] of zinc and an addition of 10 mg meso-zeaxanthin; n ¼ 60) or group 2 (Age-Related Eye Disease Study 2 formulation with a low dose[25 mg] of zinc; n ¼ 61). Visual function was assessed using best-corrected visual acuity,contrast sensitivity (CS), glare disability, retinal straylight, photostress recovery time, readingperformance, and the National Eye Institute Visual Function Questionnaire-25. Macularpigment was measured using customized heterochromatic flicker photometry.

RESULTS. There was a statistically significant improvement in the primary outcome measure(letter CS at 6 cycles per degree [6 cpd]) over time (P ¼ 0.013), and this observedimprovement was statistically comparable between interventions (P ¼ 0.881). Statisticallysignificant improvements in several secondary outcome visual function measures (letter CS at1.2 and 2.4 cpd; mesopic and photopic CS at all spatial frequencies; mesopic glare disability at1.5, 3, and 6 cpd; photopic glare disability at 1.5, 3, 6, and 12 cpd; photostress recovery time;retinal straylight; mean and maximum reading speed) were also observed over time (P < 0.05,for all), and were statistically comparable between interventions (P > 0.05, for all).Statistically significant increases in macular pigment at all eccentricities were observed overtime (P < 0.0005, for all), and the degree of augmentation was statistically comparablebetween interventions (P > 0.05).

CONCLUSIONS. Antioxidant supplementation in patients with nonadvanced age-related maculardegeneration results in significant increases in macular pigment and improvements in CS andother measures of visual function. (Clinical trial, http://www.isrctn.com/ISRCTN13894787).

Keywords: randomized clinical trial, lutein, zeaxanthin, meso-zeaxanthin, macular pigment,age-related macular degeneration, visual function, visual acuity, contrast sensitivity, macularpigment, NEI VFQ-25, photostress recovery time, reading performance, glare disability, retinalstraylight

AMD is a multifactorial disease characterized by a spectrumof degenerative changes at the macula, ultimately leading to

central vision impairment in many cases. Given the growingand aging world population, the number of people sufferingfrom AMD continues to rise. Wong et al.1 estimated theprevalence of any AMD (globally) to be 8.7% in those aged 45 to85 years and predicted that the number of people afflicted withAMD worldwide will be 288 million by 2040. In the Republic ofIreland, the current prevalence of (any) AMD among personsaged 50 years and older is estimated to be 7.2%.2 Beyond the

personal suffering of those afflicted with advanced AMD, whichincludes loss of central vision and associated adverse clinicalevents such as increased risk of falls, depression, loneliness,suicide, and so on,3 the growing prevalence of AMD representsa huge socioeconomic burden to society and to health careproviders.4 To address this challenge, preventive, retarding, andvision-optimizing strategies for nonadvanced AMD need to beexplored, and prior work in diseased and nondiseased eyesindicates that the enhancement of ocular nutrition is worthpursuing in this endeavor.5

Copyright 2017 The Authors

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Meso-zeaxanthin (MZ), zeaxanthin (Z), and lutein (L)represent the three constituent carotenoids that make upmacular pigment (MP), a yellow pigment found in the macula.Their anatomic (central and prereceptorial location), biochem-ical (antioxidant and anti-inflammatory), and optical (short-wavelength [blue] light-filtering) properties make these com-pounds ideal candidates to enhance vision and protect againstAMD and its progression.5 The Age Related Eye Disease Study(AREDS) 2, published in May 2013, examined the role ofsupplementation with two of MP’s constituent macularcarotenoids (L and Z, in combination with coantioxidants) inpatients with intermediate AMD.6 The primary outcomemeasure (POM; progression to advanced AMD) in AREDS2failed to reveal a beneficial effect of supplemental L and Z.7

However, secondary analysis, where data were dichotomizedto those supplemented with L and Z versus those notsupplemented with these macular carotenoids, did demon-strate a beneficial effect in terms of progression to theadvanced form of the disease, especially in those with a lowdietary intake of these carotenoids.7 It is important to note thatAREDS2 was designed and powered to investigate the impactof supplementation with macular carotenoids plus coantiox-idants on AMD morphology and on visual acuity, whereas thecurrent trial (Central Retinal Enrichment SupplementationTrial 2 [CREST] AMD - CREST Report 2) was designed andpowered to investigate change in psychophysical (visual)function, in patients with nonadvanced AMD, followingsupplementation with the macular carotenoids plus coantiox-idants.

In terms of assessing visual function in patients with retinaldisease (including AMD), a number of studies have examinedthe impact of supplementation with macular carotenoids.8

Indeed, recent studies have reported favorable outcomes onvisual function (e.g., contrast sensitivity [CS] and glaredisability [GD]) in patients with AMD and other retinaldiseases, following supplementation with the macular carot-enoids using a formulation of MZ:L:Z in a ratio (mg/d) of10:10:2.9,10 However, given the exploratory nature of thosestudies, a double-blind randomized controlled trial (RCT) withappropriate methodology was warranted. Originally, theCREST AMD trial planned a placebo-controlled design, butfollowing publication of AREDS2, the CREST Data Safety andMonitoring Committee (DSMC) recommended that the designbe amended to reflect the new standard of care and that,accordingly, the placebo group should be replaced with anAREDS2 formula containing a lower dose of zinc (25 mg). Inthe amended protocol, we chose a lower zinc dose (25 mg)because the AREDS2 study found no efficacy-lowering effect ofreducing zinc from 80 mg to 25 mg on either visual acuity orAMD progression.7

In summary, CREST AMD was designed and conducted toinvestigate the impact of macular carotenoid supplementationwith coantioxidants on visual function in patients with non-advanced AMD during a 2-year period (ISRCTN13894787).11 Wealso investigated whether the addition of 10 mg of MZ to aformulation containing standard AREDS2 doses of L and Z and incombination with coantioxidants offered advantages/disadvan-tages in terms of a wide array of measures of visual function andMP response.

METHODS

Trial Design

Details of the CREST design and methodology have beenreported elsewhere and are briefly summarized here.11 Ethicalapproval was granted by the Research Ethics Committee of the

Waterford Institute of Technology (reference number 12/CLS/02), Waterford, Ireland, and the Ethics Committee of theEuropean Research Council (reference number 281096). Asexplained previously, following the AREDS2 report, the CRESTprotocol was amended from a placebo-controlled design to adouble-blind, head-to-head, RCT (ISRCTN13894787) in whichparticipants were randomly assigned to two parallel groups,each receiving active supplements as follows: group 1, 10 mg/dMZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/d vitamin C, 400international units (IU)/d of vitamin E, 25 mg/d zinc, and 2 mg/dcopper (Macushield Gold [Alliance Pharma PLC & AlliancePharmaceuticals Ltd, Chippenham Wiltshire, England, UK];Macuhealth Plus [MacuHealth Limited Partnership, Birmingham,MI, USA]); and group 2, 10 mg/d L, 2 mg/d Z plus 500 mg/dvitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/dcopper (AREDS2 formula with a lower dose of zinc [25 mg]custom prepared for CREST AMD and not commerciallyavailable). The group 2 intervention, therefore, represents thestandard of care (AREDS2 formula with a lower dose of zinc [25mg]), whereas group 1 also represents the same standard ofcare, but with the addition of 10 mg of MZ. All protocol changeswere approved by the DSMC and the Research EthicsCommittee of the Waterford Institute of Technology, Waterford,Ireland, and the Ethics Committee of the European ResearchCouncil (Saint-Josse-ten-Noode, Brussels, Belgium). In addition,protocol changes were published on the International StandardRCT registration website (www.isrctn.com/ISRCTN13894787)and in the published methodology11 for this project. Participantsin each group were instructed to take the study interventiondaily with a meal for 2 years. The trial was conducted at theMacular Pigment Research Group, Nutrition Research CentreIreland (Waterford, Ireland) from November 2013 (first visit offirst participant) to May 2016 (last visit of last participant).

Randomization and Intervention

Participants were randomly assigned to intervention groupsusing block randomization (block size: 4 and randomizationratio 1:1). The randomization sequence was generated by thestudy statistician (J.S.), and a pharmacist (C.K.) performedrandom allocation to intervention groups based on thisrandomization sequence at Whitfield Clinic, Waterford, Ireland.The study investigator (K.O.A.) received, from the pharmacist,a box of supplements for each study participant, labeled onlywith the participant identification number. Only at studycompletion, after a masked database review and followingdirection from the CREST DSMC, was the randomizationsequence revealed to the study investigator and other dataanalysts.

Participants

Inclusion criteria for the trial were as follows: nonadvancedAMD (1 to 8 on the AREDS 11-step severity scale12 in at leastone eye [the study eye], confirmed by the Moorfields EyeHospital Reading Centre, London, UK, an accredited retinalgrading center); best-corrected visual acuity (BCVA) of 6/12(20/40) or better in the study eye; no more than five dioptersspherical equivalent refraction in the study eye; no previousconsumption of supplements containing the macular caroten-oids (L and/or Z and/or MZ); no retinal pathology other thanAMD; and no diabetes mellitus (by self-report). The study eyecould be either the right or left eye. If both eyes exhibitednonadvanced AMD, the eye with the best BCVA was chosen asthe study eye. However, if each eye had the same BCVA andnonadvanced AMD, the right eye was selected. Each partici-pant provided written informed consent of their willingness toparticipate in the trial, and the examination procedures

Antioxidant Interventions in Nonadvanced AMD IOVS j October 2017 j Vol. 58 j No. 12 j 5348


adhered to the tenets of the Declaration of Helsinki. Clinicalassessment was conducted at baseline and at six monthlyintervals during a 2-year period by the study investigator(K.O.A.) who was trained in all aspects of the CREST protocol.Retinal photographs were graded in a masked fashion at theMoorfields Eye Hospital Reading Centre, adhering to theAREDS 11-step severity scale.12

Outcomes

The POM was change in CS at 6 cycles per degree (cpd)following 24 months of supplementation (letter CS at 6 cpd).The Test Chart 2000PRO (Thomson Software Solutions,Hatfield, UK) was used to assess the POM. Letter CS (insteadof grating CS) at 6 cpd was chosen as our primary outcomemeasure because this measure is close to the peak contrastsensitivity function, and any improvements in CS is bestassessed at this spatial frequency. Furthermore, pilot data wereonly available on letter CS (but not grating CS), and thisinformed our choice in the current study. Secondary outcomemeasures included change in CS at the other spatialfrequencies, BCVA, GD, photostress recovery time (PRT), MP,retinal straylight, reading acuity, reading speed, subjectivevisual function (National Eye Institute Visual Function Ques-tionnaire–25 [NEI VFQ-25]), and AMD morphology. Formeasuring BCVA and letter CS, a Hewlett-Packard monitorLV916AA2211 (Hewlett-Packard, Palo Alto, CA, USA; resolution1920 3 1080, luminance 250 cd/m2, dynamic contrast ratio3,000,000: 1) was used. Prior to use for vision testing, thedevice was calibrated in accordance with the instructionsmanual from Thomson Software Solutions. Furthermore, allvision testing was conducted in the same room during thecourse of the study.

Compliance and Adverse Event Reporting

Compliance was assessed by contacting participants viatelephone, by capsule counting, and by serum carotenoidanalysis at the end of the study. Participants were also phonedregularly to ascertain whether they had experienced anyunusual signs/symptoms during the course of the study.Potential or perceived adverse events were documented andreported to the DSMC.

Statistical Analysis

A previous report described the sample size/power calculationfor this study.11 Based on an effect size of 0.15 logCS units (oneline on a letter CS chart) for the POM, and a two-tailed test atthe 5% level of significance, we estimated that 56 participantsper intervention group were needed to achieve a power of 80%for the comparison of the two intervention groups. One eye(the study eye) of each participant comprised the unit ofanalysis. Statistical analysis was performed using IBM SPSSStatistics for Windows, version 22.0 (Armonk, NY, USA). Allanalyses were conducted as per protocol. However, intention-to-treat (ITT) analysis was also performed, and discrepanciesbetween ITT analyses and per protocol are reported herein. Nointerim analyses were conducted during the course of thestudy.

Baseline differences between intervention groups wereassessed using independent samples t-tests for intervalvariables and contingency table analyses using the chi-squaredtests for categorical variables.

Most of the outcome variables in this study were changes(over time) in interval variables (e.g., CS, MP). To compare theeffects of the two intervention groups (on each intervaloutcome measure, over time), we used repeated measures

analysis of variance, with time as a within-participants factorand intervention group as a between-participants factor. In theITT analysis, the last observation carried forward was usedwhen participant data were missing.

Tests of significance, for all comparisons of interventiongroups on interval outcome measures, were two-tailed, and the5% level of significance was used throughout. We did notcorrect for multiple tests, as we were anxious to avoid type IIerrors.

RESULTS

Figure 1 shows the Consolidated Standards of Reporting Trialsdiagram,13 summarizing the CREST study design, participantenrolment, randomization, follow-up, and the number ofparticipants included in study analyses. In this study, 121participants were enrolled at baseline with 98 participantscompleting final assessment at 24 months. Baseline character-istics (see Table 1) were statistically comparable betweeninterventions, except for letter CS (1.2 and 2.4 cpd) andphotopic CS at 3 cpd. Losses to follow-up after 2 years ofantioxidant supplementation were statistically comparablebetween interventions (P ¼ 0.680, Pearson chi-square).

Primary Outcome Measure

The repeated measures analysis of change in letter CS at 6cpd (POM) is presented in Table 2 (as per protocol). Therewas a statistically significant improvement in the POMduring the study period (P ¼ 0.013 for time effect), butthere was no statistically significant difference between theintervention groups (P ¼ 0.881 for the time 3 groupinteraction effect). Thus, there is no evidence that the twointervention groups are different with respect to improve-ment in this measure. Figure 2 graphically illustrates thesefindings.

Secondary Outcome Measures

Other Visual Function Outcomes From Baseline to 24Months. Results from the repeated measures analysis, forother visual function variables, are also shown in Table 2.There was a statistically significant improvement (P < 0.05, fortime effect) in most measures of visual function (75%; 24 of 32of vision-related outcome measures) during the study period,including CS, PRT, retinal straylight, and GD, and again theseimprovements were statistically comparable between interven-tion groups (P > 0.05). There was one exception; mesopic GDat 3 cpd (P ¼ 0.040 for the time 3 group interaction effect),which improved to a borderline significantly greater extent ingroup 2. However, in the subsequent ITT analysis, the disparitybetween interventions in terms of mesopic GD at 3 cpd was nolonger significant (P ¼ 0.132 for the time 3 group interactioneffect). Figures 2, 3, and 4 graphically illustrate these findings.

Clinically Significant Contrast Sensitivity Findings

The numbers and proportions of patients exhibiting clinicallymeaningful changes (one line or more on a letter CS chart) arepresented in Table 3, where it is evident (especially for CS at1.2 and 2.4 cpd, but also for the POM) that the percentage ofparticipants showing a clinically meaningful improvement inCS over time greatly exceeds the percentage showing aclinically significant deterioration, and that this observation istrue for each intervention group.

Macular Pigment From Baseline to 24 Months. Therewas a statistically significant increase in MP for all eccentric-



ities during the course of the study (P < 0.0005, for all time

effects), but this increase was statistically comparable betweenintervention groups (P > 0.05 for time 3 group interactioneffect at all retinal eccentricities; Table 4). Figure 5 graphically

illustrates these findings.

Serum Carotenoids From Baseline to 24 Months. Therewas a statistically significant increase in serum concentrations of

L, Z, and MZ during the course of the study (P < 0.0005, for alltime effects; Table 4). The repeated measures analysis of changein serum L concentrations over time did not show significant

differences between intervention groups (P¼ 0.111 for the time3 group interaction effect). Observed increases in serum Z

concentrations were significantly greater in group 2 when

compared with group 1 (P ¼ 0.005 for the time 3 group

interaction effect). Significant increases in serum MZ concen-trations were observed in group 1, but not in group 2 (P <0.0005 for the time 3 group interaction effect). In terms of

observed increases in total (composite) serum macular caroten-oid concentrations (i.e., L, Z, and MZ combined), this measureincreased significantly over time, and no significant difference

between intervention groups (P ¼ 0.241 for the time 3 groupinteraction effect) was observed. Figure 6 graphically illustrates

these findings.

Grade of AMD From Baseline to 24 Months. Table 5shows, within each intervention group, the transition between

these grades from baseline to final study visit at 24 months.

FIGURE 1. CREST AMD consolidated standards of reporting trials flow diagram. d, Participants declined to participate either due to personalreasons, transportation difficulties, or cataract surgery; *, Participants were initially enrolled based on nondetail grading of retinal photographsobtained at screening visit, confirming eligibility by the Moorfields Eye Hospital Reading Centre. However, detailed grading of baseline retinalphotographs showed some participants had AMD grades > 8 on the AREDS 11-step severity scale and therefore these participants were excludedbased on a decision by the DSMC.



TABLE 1. Baseline Characteristics by Intervention Group in the CREST AMD Study (Per Protocol)

Variables Group 1, n ¼ 57* Group 2, n ¼ 61† Sig.

Demographic, lifestyle, and health

Age, y 65.09 6 8.59 64.34 6 9.50 0.657

Body mass index, kg/m2 28.27 6 4.30 27.78 6 4.57 0.551

Blood pressure, mm Hg

Systolic 142.07 6 20.98 138.00 6 24.35 0.334

Diastolic 82.65 6 11.21 79.12 6 9.81 0.070

Sex

Male 18 (45.0) 22 (55.0) 0.607

Female 39 (50.0) 39 (50.0)

Education

Primary 7 (43.8) 9 (56.3) 0.766

Secondary 29 (51.8) 27 (48.2)

Tertiary 21 (45.7) 25 (54.3)

Smoking

Never 29 (50.0) 29 (50.0) 0.933

Past 23 (46.9) 26 (53.1)

Current 5 (45.5) 6 (54.5)

AMD family history

Yes 16 (53.3) 14 (46.7) 0.406

No 31 (44.3) 39 (55.7)

Cardiovascular disease

Yes 5 (50.0) 5 (50.0) 0.804

No 50 (47.6) 55 (52.4)

Hypertension

Yes 17 (48.6) 18 (51.4) 0.970

No 40 (48.2) 43 (51.8)

AMD grades

1-3 13 (43.3) 17 (56.7) 0.528

4-8 44 (50.0) 44 (50.0)

Diet score 26.90 6 12.00 26.26 6 12.03 0.776

Serum carotenoids*

Serum L, lmol/l 0.35 6 0.20 0.34 6 0.22 0.710

Serum Z, lmol/l 0.07 6 0.05 0.07 6 0.05 0.639

Serum MZ, lmol/l 0.00 6 0.01 0.01 6 0.02 0.205

Macular pigment

Densitometer*

0.258 0.79 6 0.24 0.72 6 0.26 0.179

0.58 0.65 6 0.22 0.60 6 0.21 0.204

1.08 0.45 6 0.16 0.45 6 0.17 0.927

1.758 0.32 6 0.12 0.31 6 0.15 0.933

Vision

Best corrected visual acuity, VAR

Study eye 100.04 6 5.83 100.08 6 5.62 0.965

Fellow eye 94.63 6 10.95 95.92 6 12.20 0.549

Letter contrast sensitivity, LogCS

1.2 cpd 1.77 6 0.17 1.85 6 0.16 0.007

2.4 cpd 1.76 6 0.21 1.83 6 0.18 0.045

6 cpd, POM 1.49 6 0.25 1.56 6 0.21 0.108

9.6 cpd 1.23 6 0.30 1.32 6 0.25 0.082

15.15 cpd* 0.86 6 0.35 0.94 6 0.29 0.160

Mesopic contrast sensitivity, LogCS

1.5 cpd 1.53 6 0.22 1.61 6 0.21 0.065

3 cpd 1.62 6 0.23 1.68 6 0.18 0.106

6 cpd 1.21 6 0.35 1.33 6 0.35 0.065

12 cpd 0.78 6 0.27 0.85 6 0.28 0.132

18 cpd 0.33 6 0.12 0.32 6 0.11 0.749



Importantly, no participant from Group 1 (the interventioncontaining MZ) and only one participant from Group 2progressed to advanced AMD over the study period.

Compliance

The compliance to study intervention (as measured by capsulecounting) was not significantly different between interventiongroups during the course of the study (P¼0.342 for the time 3group interaction effect). In addition, serum carotenoidassessment indicated good compliance to study intervention(see Fig. 6).

Adverse Events

The distribution of potential or perceived adverse eventsreported during the course of the study is shown in Table 6.

Some participants reported more than one adverse event. Theproportion of participants experiencing any adverse event wasstatistically similar between interventions: 15 (26%) of 57 fromgroup 1 and 10 (16%) of 61 from group 2 (P¼ 0.187, Pearsonchi-squared test). No serious adverse event relating to the studyintervention was reported in either intervention group duringthe course of the study.

DISCUSSION

This RCT was designed to compare the impact of two differentmacular carotenoid formulations, in combination with coan-tioxidants, on visual function in patients with nonadvancedAMD. The AMD disease status of participants was graded usingthe AREDS 11-step severity scale12 and included only eyes

TABLE 1. Continued

Variables Group 1, n ¼ 57* Group 2, n ¼ 61† Sig.

Photopic contrast sensitivity, LogCS

1.5 cpd 1.46 6 0.19 1.52 6 0.16 0.061

3 cpd 1.72 6 0.22 1.80 6 0.19 0.047

6 cpd 1.58 6 0.31 1.68 6 0.31 0.079

12 cpd 1.19 6 0.38 1.27 6 0.35 0.279

18 cpd 0.51 6 0.34 0.62 6 0.34 0.081

Mesopic glare disability, LogCS

1.5 cpd 0.91 6 0.32 0.99 6 0.29 0.193

3 cpd 1.11 6 0.37 1.19 6 0.32 0.241

6 cpd 0.93 6 0.25 0.93 6 0.23 0.977

12 cpd 0.66 6 0.15 0.63 6 0.11 0.355

18 cpd 0.30 6 0.00 0.31 6 0.04 0.336

Photopic glare disability, LogCS

1.5 cpd 1.40 6 0.21 1.46 6 0.17 0.082

3 cpd 1.67 6 0.22 1.73 6 0.18 0.130

6 cpd 1.51 6 0.32 1.58 6 0.31 0.210

12 cpd 1.11 6 0.36 1.19 6 0.36 0.206

18 cpd 0.52 6 0.35 0.56 6 0.31 0.583

Retinal Straylight 1.30 6 0.18 1.33 6 0.25 0.381

Photostress recovery time, s 15.98 6 8.72 15.97 6 7.99 0.996

Reading performance

Reading acuity, LogRAD 0.12 6 0.13 0.09 6 0.12 0.165

Mean reading speed, w/min 154.48 6 26.82 156.45 6 27.53 0.694

Maximum reading speed, w/min 199.61 6 31.58 201.56 6 34.44 0.749

National Eye Institute Questionnaire-25

Overall vision score 87.80 6 9.96 90.38 6 9.22 0.147

Data displayed are mean 6 standard deviation for interval data and percentages, n (%), for categorical data; the percentages displayed are rowpercentages. Sig., significance set at P < 0.05. Education, highest level of education; Smoking, Never (<100 cigarettes in lifetime), Past (smoked ‡100cigarettes in lifetime and none in past year), current (smoked ‡100 cigarettes in lifetime and at least one in the last year). *, n „ 57 in group 1 and/or n „61 in group 2 as certain tests/measures were not obtained. VAR, visual acuity rating. VAR¼ 100� 50 LogMAR, a score of 100 corresponds with 20/20 (6/6); LogCS, logarithm of contrast sensitivity units. Family history of AMD means having a first degree relative, that is, parent or sibling, with AMD AREDS 11-step scale. Diet score, estimated dietary intake of lutein and zeaxanthin using the ‘‘L/Z screener’’ developed by Professor Elizabeth Johnson, TuftsUniversity. Macular pigment measured using the Macular Densitometer (Macular Metrics Corp.). Serum macular carotenoids analyzed by HPLC. Best-corrected visual acuity measured with the Test Chart 2000 Xpert (Thomson Software Solutions). Letter contrast sensitivity measured using the Test Chart2000 PRO (Thomson Software Solutions). Mesopic and photopic contrast sensitivity measured using the Functional Vision Analyzer (Stereo Optical Co.).Mesopic and photopic glare disability measured using the Functional Vision Analyzer (Stereo Optical Co.). Retinal straylight measured using the Oculus C-Quant (Oculus GmbH, Wetzler, Germany) and recorded in logarithms (judged reliable when estimated standard deviation (ESD) � 0.08 and Q ‡ 1).Photostress recovery time measured by assessing the time of recovery after a 10-second exposure to a 300-watt tungsten spotlight (ARRI 300 Plus lamp,ARRI Lighting Solutions GmbH, Berlin, Germany) with a low-pass glass dichroic filter. Reading performance assessed using the English version of thestandardized Radner reading chart at a distance of 40 cm with reading correction. Reading acuity recorded in logarithm of the reading acuitydetermination (LogRAD). The following formula was used to calculate the LogRAD-score: logRADþ total number of incorrectly read syllables 3 0.005.Reading speed (the time taken to read the number of words in a sentence) was measured in words per minute (w/min) with a stop watch for eachstandardized sentence (14 words3 60 seconds divided by reading time in seconds). National Eye Institute Visual Function Questionnaire–25 overall visionscores range from zero (worst) to 100 (best).

* Group 1, 10 mg/d MZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper.† Group 2, 10 mg/d L, 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper.



TABLE 2. Repeated Measures Analysis of Visual Function Outcomes From Baseline to 24 Months in the CREST AMD Study by Intervention Groups

Variable N

Group 1*

N

Group 2† Time Time 3 Group

Baseline 24 Months Baseline 24 Months Effect Interaction

Mean SD Mean SD Mean SD Mean SD Sig. Sig.

Vision

Best corrected visual acuity, VAR 46 101.22 5.16 100.91 5.80 51 100.78 5.08 101.31 5.20 0.746 0.233

Letter contrast sensitivity, LogCS

1.2 cpd 46 1.79 0.17 1.89 0.20 51 1.86 0.14 1.91 0.16 <0.0005 0.058

2.4 cpd 46 1.78 0.22 1.86 0.22 51 1.85 0.16 1.91 0.18 <0.0005 0.582

6 cpd, POM 46 1.53 0.24 1.57 0.29 51 1.58 0.18 1.61 0.23 0.013 0.881

9.6 cpd 46 1.29 0.28 1.31 0.30 51 1.36 0.21 1.38 0.26 0.154 0.925

15.15 cpd 46 0.92 0.33 0.95 0.34 51 0.96 0.27 1.01 0.33 0.082 0.747

Mesopic contrast sensitivity, LogCS

1.5 cpd 46 1.55 0.22 1.62 0.24 51 1.63 0.21 1.70 0.23 0.007 0.982

3 cpd 46 1.63 0.24 1.76 0.27 51 1.69 0.18 1.84 0.27 <0.0005 0.523

6 cpd 46 1.25 0.35 1.48 0.45 51 1.34 0.34 1.49 0.42 <0.0005 0.228

12 cpd 46 0.81 0.29 0.94 0.36 51 0.87 0.28 0.96 0.35 0.002 0.605

18 cpd 46 0.33 0.13 0.39 0.23 51 0.31 0.08 0.41 0.25 <0.0005 0.369

Photopic contrast sensitivity, LogCS

1.5 cpd 46 1.47 0.19 1.60 0.23 51 1.53 0.16 1.64 0.21 <0.0005 0.862

3 cpd 46 1.75 0.23 1.84 0.23 51 1.82 0.18 1.91 0.21 <0.0005 0.986

6 cpd 46 1.63 0.28 1.74 0.39 51 1.70 0.29 1.81 0.34 <0.0005 0.934

12 cpd 46 1.25 0.37 1.34 0.43 51 1.30 0.33 1.34 0.37 0.015 0.468

18 cpd 46 0.56 0.36 0.71 0.44 51 0.65 0.34 0.69 0.36 0.008 0.174

Mesopic glare disability, LogCS

1.5 cpd 46 0.98 0.32 1.08 0.44 51 1.01 0.29 1.20 0.45 <0.0005 0.172

3 cpd 46 1.19 0.36 1.22 0.43 51 1.22 0.30 1.38 0.41 0.001 0.040

6 cpd 46 0.97 0.27 1.05 0.35 51 0.94 0.23 1.09 0.35 <0.0005 0.222

12 cpd 46 0.67 0.16 0.68 0.22 51 0.64 0.12 0.69 0.18 0.133 0.412

18 cpd 46 0.30 0.00 0.32 0.10 51 0.31 0.04 0.31 0.08 0.197 0.486

Photopic glare disability, LogCS

1.5 cpd 46 1.43 0.21 1.55 0.26 51 1.47 0.18 1.55 0.24 <0.0005 0.364

3 cpd 46 1.70 0.22 1.82 0.25 51 1.74 0.18 1.83 0.24 <0.0005 0.542

6 cpd 46 1.56 0.31 1.65 0.40 51 1.61 0.29 1.70 0.34 0.001 0.987

12 cpd 46 1.18 0.34 1.26 0.41 51 1.23 0.33 1.31 0.38 0.011 0.913

18 cpd 46 0.58 0.37 0.60 0.39 51 0.57 0.31 0.62 0.33 0.179 0.646

Retinal Straylight, Logs 41 1.29 0.18 1.25 0.19 43 1.33 0.20 1.26 0.16 0.004 0.359

Photostress recovery time, s 46 16.93 9.19 12.47 6.79 51 16.00 8.51 10.96 6.05 <0.0005 0.757

Reading performance

Reading acuity, LogRAD 46 0.09 0.12 0.09 0.08 51 0.07 0.10 0.06 0.10 0.637 0.759

Mean reading speed, w/min 46 154.61 27.11 189.89 26.53 51 158.75 27.00 192.82 28.54 <0.0005 0.765

Maximum reading speed, w/min 46 200.44 32.25 244.00 35.02 51 204.74 33.40 245.38 37.90 <0.0005 0.606

National Eye Institute Questionnaire-25

Overall vision score 46 89.24 7.95 89.27 9.61 50 90.83 9.66 91.93 7.01 0.408 0.434

N, participants with data at all study visits; Sig., significance set at P < 0.05. P values obtained from repeated measures analysis of variance. Best-corrected visual acuity measured with the Test Chart 2000 Xpert (Thomson Software Solutions). Letter contrast sensitivity measured using the TestChart 2000 PRO (Thomson Software Solutions). Mesopic and photopic contrast sensitivity measured using the Functional Vision Analyzer (StereoOptical Co.). Mesopic and photopic glare disability measured using the Functional Vision Analyzer (Stereo Optical Co.). Retinal straylight measuredusing Oculus C-Quant (Oculus GmbH) and recorded in logarithms (judged reliable when ESD � 0.08 and Q ‡ 1). Photostress recovery timemeasured by assessing the time of recovery after a 10-second exposure to a 300-watt tungsten spotlight (ARRI 300 Plus lamp) with a low-pass glassdichroic filter. Reading performance assessed using the English version of the standardized Radner reading chart at a distance of 40 cm with readingcorrection. Reading acuity recorded in logarithm of the reading acuity determination (LogRAD). The following formula was used to calculate theLogRAD score: logRAD þ total number of incorrectly read syllables 3 0.005. Reading speed (the time taken to read the number of words in asentence) was measured in words per minute (w/min) with a stop watch for each standardized sentence (14 words 3 60 seconds divided by readingtime in seconds). National Eye Institute Visual Function Questionnaire–25 overall vision scores range from zero (worst) to 100 (best).




classed as grade 1 to 8 at baseline (referred to as nonadvancedAMD for the purpose of the current study). We did not includeeyes with noncentral geographic atrophy (AMD grade 9 on theAREDS 11-step severity scale). Given the biologically plausiblerationale that benefits, in terms of vision and in terms of MPaugmentation, are more likely to extend to participants with

earlier disease (before irreversible damage has occurred, suchas in noncentral geographic atrophy [grade 9 AREDS 11-stepseverity scale]), we purposely recruited eyes at an earlier stageof disease. We report improvements in a range of measures ofvisual function (i.e., CS, GD, PRT, reading speed) followingsupplementation with the macular carotenoids in combination

FIGURE 2. Letter contrast sensitivity function using the Test Chart 2000 PRO (Thomson Software Solutions) in the CREST AMD study. Group 1, 10mg/d MZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper; group 2, 10 mg/d L, 2 mg/d Zplus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper. Error bars represent standard error of mean.

FIGURE 3. Mesopic and photopic contrast sensitivity function using the Functional Vision Analyzer (Stereo Optical Co., Chicago, IL, USA) in theCREST AMD study. Group 1, 10 mg/d MZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/dcopper; group 2, 10 mg/d L, 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper. Error bars representstandard error of mean.



with coantioxidants, and our results are consistent with

previous studies.9,14,15

A possible explanation for the role that MP plays in

optimizing CS rests on the visibility hypothesis of MP, which

posits that this prereceptorial pigment enhances visualiza-

tion of a target’s detail by the absorption of blue haze.16 Blue

haze is a subjective experience and is caused by scattered

short-wavelength dominant air light (blue light), which

results in a veiling luminance when we view objects at a

distance.16 MP accentuates the luminance of an object

relative to its background by attenuating the impact of this

scattered (veiling) short-wavelength visible blue light on the

FIGURE 4. Mesopic and photopic glare disability using the Functional Vision Analyzer (Stereo Optical Co.) in the CREST AMD study. Group 1, 10mg/d MZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper; group 2, 10 mg/d L, 2 mg/d Zplus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper. Error bars represent standard error of mean.

FIGURE 5. Macular pigment response in the CREST AMD study. Group 1, 10 mg/d MZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/dof vitamin E, 25 mg/d zinc, and 2 mg/d copper; group 2, 10 mg/d L, 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2mg/d copper. Macular pigment measured using a Macular Densitometer (Macular Metrics Corp., Providence, RI, USA). Error bars representstandard error of mean.



just noticeable differences of luminance required fordiscernibility and, by consequence, extends the visualrange.17 Indeed, the visibility hypothesis has been testedempirically and is supported by two studies that havedemonstrated the beneficial effect of MP in this respectunder simulated blue haze conditions.18,19 Beyond thisoptical effect, the macular carotenoids may also favorablyinfluence lateral inhibitory mechanisms20 and may therebyhave contributed to the observed improvements in CSfollowing supplementation.

Importantly, we believe that the observed improvements inCS in this trial are clinically meaningful. Recently, Maynard etal.21 demonstrated that, when compared with age-similarhealthy eyes, patients with nonadvanced AMD exhibit signif-icantly worse CS (reflecting a deterioration of �0.007 log CS/year), consistent with the findings of a major review by Neelamet al.22 In terms of visual performance, visual acuity is ameasure of the ability to correctly identify targets (of variablesize) at 100% contrast, whereas CS is a measure of the ability todetect/identify targets (of variable sizes [spatial frequencies]) atvarying contrast (i.e., faintness). Furthermore, CS (but notBCVA) can effectively predict how well patients see targetstypical of everyday life, which has important implications forquality of life.23 Consequently, good visual acuity in the

presence of poor CS (e.g., nonadvanced cataract) results inreports of visual complaints,24 particularly for real-world tasksand targets,23 but the following question remains: what degreeof change in CS will have a clinically meaningful impact for thepatient?

For VA, a one-line change (0.1 log MAR) is consideredclinically meaningful.25 For CS, the available data indicate that a0.1 log change in the percentage threshold contrast requiredfor the detection of a target/pattern is equally (if not more)devastating to visual performance than a deterioration of oneline of BCVA.23,26 In brief, threshold contrast is the contrastrequired to see the target reliably; the reciprocal of threshold iscalled sensitivity, which is expressed as a percentage (e.g., seeMichelson contrast).27 For example, for spatial frequencies thatare near the peak of the contrast sensitivity function (i.e., 4–6cycles/degree), younger and middle-aged patients have con-trast thresholds of, on average, circa 2.5%. A 0.1 log unitdeterioration from this value yields a contrast threshold of3.2%, which is classed as visual impairment.28 Moreover,contrast thresholds > 5% are associated with increased risk ofdriving accidents.28 Accordingly, a decrease/increase in CS of0.1 log unit is deemed clinically meaningful; in this study,19.6% to 34.8% of participants exhibited at least this magnitudeof improvement at three spatial frequencies, whereas this

TABLE 3. Change in Contrast Sensitivity of ‡1 Line of CS

Variable

% Showing

Clinical

Improvement

% Showing

Clinical

Deterioration

Group 1* Group 2† Group 1* Group 2†

Letter CS 1.2 cpd 34.8 19.6 2.2 3.9

Letter CS 2.4 cpd 26.1 21.6 4.3 3.9

Letter CS 6 cpd 26.1 21.6 13 11.8

Clinical significance, which for present purposes we defined as oneline or more on a letter CS chart. Letter CS measured using the TestChart 2000 PRO (Thomson Software Solutions).

* Group 1, 10 mg/d MZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/dvitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2 mg/d copper.

† Group 2, 10 mg/d L, 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/dof vitamin E, 25 mg/d zinc, and 2 mg/d copper.

TABLE 4. Repeated Measures Analysis of Macular Pigment and Serum Carotenoid Outcomes From Baseline to 24 Months in the CREST AMD Studyby Intervention Group

Variable N

Group 1*

N

Group 2† Time Time 3 Group

Baseline 24 Months Baseline 24 Months Effect Interaction

Mean SD Mean SD Mean SD Mean SD Sig. Sig.

Macular pigment

0.258 45 0.80 0.23 1.02 0.15 50 0.72 0.25 1.00 0.16 <0.0005 0.247

0.58 45 0.67 0.23 0.90 0.14 50 0.60 0.22 0.88 0.15 <0.0005 0.334

1.08 45 0.44 0.17 0.66 0.11 50 0.45 0.18 0.63 0.09 <0.0005 0.444

1.758 45 0.32 0.12 0.44 0.10 50 0.31 0.16 0.43 0.13 <0.0005 0.924

Serum carotenoids

Serum L, lmol/l 41 0.34 0.16 1.40 0.83 47 0.33 0.21 1.72 1.06 <0.0005 0.111

Serum Z, lmol/l 40 0.07 0.04 0.14 0.07 46 0.07 0.05 0.19 0.11 <0.0005 0.005

Serum MZ, lmol/l 40 0.00 0.01 0.10 0.08 46 0.00 0.01 0.00 0.01 <0.0005 <0.0005

Serum TC, lmol/l 40 0.41 0.20 1.65 0.96 46 0.40 0.26 1.91 1.18 <0.0005 0.241

Macular pigment measured using the Macular Densitometer (Macular Metrics Corp.). Serum macular carotenoids analyzed by HPLC. Totalcarotenoids represent the total (composite) serum macular carotenoid concentrations (i.e., L, Z, and MZ combined). N, participants with data at allstudy visits. Sig., Significance set at P < 0.05.


TABLE 5. Change in AMD Morphology in the CREST AMD Study byIntervention Group

Study Visit Intervention

Low

Risk

High

Risk

Advanced

AMD Total

Baseline Group 1* 13 44 0 57

Group 2† 17 44 0 61

24 months Group 1* 11 35 0 46

Group 2† 11 38 1 50

Low risk, AMD grades 1 to 3 on the AREDS 11-step scale; high risk,AMD grades 4 to 8 on the AREDS 11-step scale; advanced AMD, AMDgrades 9 to 11 on the AREDS 11-step scale.





magnitude of deterioration was demonstrable in only 2.2% to13% of participants at the same three spatial frequencies.

GD, defined as reduction in visual function caused by aglare source, results in retinal contrast loss secondary to retinalstraylight.29,30 Clinically, GD can be measured by assessing theimpact of a glare source on visual function (BCVA or CS) or bythe measurement of retinal straylight.30 Of note, the Commis-sion Internationale de l’Eclairage defines GD in terms of retinalstraylight.29 For the purposes of this study, GD was measuredusing each of these aforementioned methods (i.e., by assessingCS under conditions of glare [in both mesopic and photopicconditions] using the Functional Vision Analyzer and bymeasuring retinal straylight using the Oculus C-Quant).Mechanisms put forward to explain the observed improve-ments in CS following MP augmentation in patients withnonadvanced AMD apply also to the observed improvementsin GD in this population, but with the possibility of anadditional element, which relates the glare hypothesis of MP.31

The glare hypothesis of MP posits that MP augmentationshould improve GD and PRT via its optical (blue light) filtrationproperties.31 Of note, the absorption spectrum of MP32

accounts for one third of the visible spectrum, and wave-lengths of light responsible for GD are those in MP’s absorptionrange.31 Therefore, and given that MP filters short-wavelengthlight at a prereceptorial level, thereby reducing the adverseimpact of retinal straylight (caused by the glare source) that

casts a veiling luminance on the retina, the observedimprovements in CS under conditions of glare (GD) areunsurprising.31 Also, improvements in PRT following supple-mentation may also be explained, at least in part, by the glarehypothesis of MP.31 In brief, MP attenuates short-wavelengthlight from the glare source before it reaches the photorecep-tors, thereby reducing its impact on photopigment bleaching,and, consequently, reducing the recovery time (i.e., the time ittakes for vision to be restored).

The observed improvement in reading speed as a conse-quence of supplementation may be attributed to visual and/ornonvisual (neurocognitive) factors. In terms of the visualfactors, reading speed is a function of both spatial andtemporal CS,33 and we have already discussed the mechanismswhereby antioxidant supplementation resulted in an improve-ment in two aspects of spatial vision (CS and GD). In terms oftemporal vision, it has been shown that MP is positively relatedto critical flicker fusion frequency and to the full temporal CSfunction measured at the fovea but not the parafovea.34

Furthermore, supplemental macular carotenoids have beenshown to increase critical flicker fusion frequency thresholdsand visual motor reaction time in young healthy participants.35

Thus, MP could improve reading speed by its effects ontemporal vision (i.e., increasing temporal processing speeds).Indeed, Stringham and Stringham36 have suggested thattemporal visual mechanisms compensate for MP’s optical

FIGURE 6. Serum carotenoid response in the CREST AMD study. Group 1, 10 mg/d MZ, 10 mg/d L, and 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/dof vitamin E, 25 mg/d zinc, and 2 mg/d copper; group 2, 10 mg/d L, 2 mg/d Z plus 500 mg/d vitamin C, 400 IU/d of vitamin E, 25 mg/d zinc, and 2mg/d copper. Serum macular carotenoids analyzed by HPLC. Serum total macular carotenoids represent the addition of serum lutein, zeaxanthin,and meso-zeaxanthin concentrations obtained at each study visit. Error bars represent standard error of mean.



filtration properties by reducing temporal input from the short-wavelength cone system and increasing temporal processingby the middle/long wavelength cone system. These aspects oftemporal vision may be enhanced following supplementationwith the macular carotenoids35 and may lead to subsequentimprovements in reading speed.

Vision-related quality of life questionnaires are known tocorrelate with subjective measures of visual function (e.g., CSand reading speed),37 and, therefore, it is likely thatimprovements in these parameters will result in improvedquality of life. Scilley et al.38 reported that persons withnonadvanced AMD have good visual acuity, but are likely tohave problems with night driving, near vision tasks, and GDwhen compared with persons with no retinal disease (age-matched controls with normal retinal health). Visual acuity, CS,and reading speed are known determinants of vision-relatedquality of life in patients with nonadvanced AMD,39 reflectedin the findings of the Los Angeles Latino Eye Study, wherenonadvanced AMD lesions (i.e., soft indistinct drusen andpigmentary abnormalities) were associated with a lower self-reported vision-related quality of life.40 Therefore, the ob-served improvements in visual function parameters (in the

current study) are likely to impact favourably on quality of lifeof patients with nonadvanced AMD. However, our vision-related quality of life instrument (NEI VFQ-25) did not showany statistically significant improvements following supple-mentation with macular carotenoids (in combination withcoantioxidants), and we suspect that a larger number ofparticipants will be required to do so with such an instrument.For instance, to detect a two-point difference betweeninterventions in the NEI VFQ-25 overall score (assuming a 5%level of significance, 80% power ,and two-tailed test), therequired sample size would be 3136 participants (1568 perintervention group).41

Eye care professionals should be aware of the observedvisual benefits afforded to patients with nonadvanced AMD as aresult of supplementation with macular carotenoids (andcoantioxidants) in the short, medium, and long terms, andthe indication for recommending such supplements should nolonger be limited to risk reduction for disease progression inthe long term. Also, and importantly, further augmentation ofMP and further improvements in psychophysical function arerealized in patients with nonadvanced AMD after 24 months ofsustained supplementation, and it may well be that theimprovements observed in this study (duration of 24 months)understate the visual improvements that patients can expect.9

Given that psychophysical function is compromised innonadvanced AMD in a way that is commensurate with thestage of nonadvanced AMD and given that AMD is a progressivedisease, our findings of visual improvements in a conditionwhere visual deterioration is expected is as interesting as it iswelcome. If psychophysical visual function can be improved ina progressive condition (such as nonadvanced AMD), it istempting to hypothesize that improvements in psychophysicalfunction herald regression of the morphological changes thatunderpin them. However, longer term studies with largernumbers of patients with nonadvanced AMD, and with regularmonitoring of MP and psychophysical function as well asmorphological changes, are required to confirm or refute thishypothesis.

It is possible that some of our reported improvements inpsychophysical measures of visual function (e.g., readingspeed) may be due to learning effects, but given that we hadno placebo group (which represents a limitation of our study)it is difficult to ascertain to what level (if any). It is alsoimportant to point out that reading speed was not a primaryoutcome measure in this trial. However, given the long periodsof time between study visits, we feel that these learning effectsare likely to be minimal. It should also be appreciated thatthese improvements in for example, reading speed, wereobserved in patients suffering from a condition associated withprogressive visual deterioration and at a time of life whenspeed of neural processing declines.

Of note, the MP levels reported at baseline may beconsidered high.42 This suggests that the current study wasrepresentative of a very well-nourished population and thismay have, in fact, resulted in understating the benefits ofsupplementation that may have been seen in a less well-nourished population (as was the case in subgroup analyses ofthe AREDS2 cohort).43

In this study, we measured MP using two devices; namelythe Densitometer (Macular Metrics) and the Spectralis HRA-OCT MultiColor (Heidelberg Engineering, GmbH, Heidelberg,Germany). In a previous report, using data from the currentstudy, we found that measures of MP using these two devicesare not impressively concordant, although each of these twodevices is capable of detecting statistically significant changesin MP over time, within a given eye, following supplementa-tion with MP’s constituent carotenoids.44 Furthermore, anoth-er recent study has found that MP measurement using the

TABLE 6. Distribution of Adverse Events in the CREST AMD Study byIntervention Group

Adverse Events

Group 1,

n ¼ 57*

Group 2,

n ¼ 61†

Any adverse event 15 10

Ocular

Watery eyes 1 1

Transient blurred vision 1 0

Gritty eyes 1 0

Ocular pain 1

Bloodshot eyes 1 0

Nonocular

Nausea 2 3

Tiredness 2 1

Vomiting 3 0

Itchy skin 1 1

Metallic taste in mouth 1 1

Heat rash 0 2

Irritable bowel syndrome 1 0

Night-time urination 1 0

Headaches 1 0

Weight gain 1 0

Overactive kidney 0 1

Leg cramps 1 0

Knee ache 1 0

Red and swollen arms and legs 0 1

Dizziness 1 0

Neck stiffness 1 0

Abdominal pains 0 1

Pancreatitis 0 1

Palpitations 1 0

Sleep disturbance 1 0

Swollen face 0 1

Hallucinations 0 1

Swollen ankle 0 1

Loss of appetite 0 1

Data expressed as number of participants. Some participantsreported more than one adverse event.





Spectralis is affected by cataract.45 Thus, in the current study,which included patients with varying severity of lensopacification, we elected (following advice from the DSMC)to use the MP measures from the Densitometer, which arerobust to cataract.46,47

The strengths of this study include its randomized,controlled, and double-masked design, the range of parame-ters of visual function assessed, the fact that MP wasmeasured and monitored using an established and validatedtechnique, and the determination of serological responsesand that AMD was graded in a masked fashion by anaccredited reading center. Finally, the study was overseenby an independent DSMC.

A study limitation (albeit slight) is the failure to reach theintended sample size of 56 participants per group; actualsamples sizes were 51 and 46. However, because we elected touse repeated measures analysis of variance, rather than theindependent-samples t-tests on which the original sample sizecalculations had been based, our statistical tests (of time andtime 3 supplement interaction effects) were based on the t-distribution with more than 90 degrees of freedom, that is,these tests were more than adequately powered.

Another study limitation is the absence of a placebo arm.However, as already noted, the original study protocol had a trueplacebo, but that protocol had to be revised on ethical grounds,following publication of the AREDS2 findings. We did notmeasure the serum concentrations of any of the co-antioxidants(vitamin C, E, zinc, and copper) in this RCT. We do, however,report serum response of the macular carotenoids, which wasimportant in the assessment of compliance, and that allowed usto investigate whether participants were responding to thenutrients of interest. Assessing the concentrations of thecoantioxidants may have yielded insights into the interrelation-ships/interactions between these compounds and the macularcarotenoids, and future studies may consider adopting such anapproach. Correction for multiple testing was not performed inthe current study. It is therefore possible that some of ourreported significant results may be attributable to type 1 errors.However, many of the reported P values in this study would stillbe significant after Bonferroni adjustment.

In summary, supplementation with a formulation thatcontains the macular carotenoids (with or without MZ), incombination with coantioxidants, results in improvements incontrast sensitivity and other measures of visual function inpatients with nonadvanced AMD.

Acknowledgments

The authors thank the Whitfield Clinic Pharmacy, Waterford,Ireland, for their support with randomization and interventionassignment (Catherine Kelly [Chief Pharmacist] and Lisa O’Brien[Pharmacy Technician]). They also thank Moorfields Eye HospitalReading Centre, London, United Kingdom, for retinal photographgrading where Tunde Peto and Irene Leung have been funded bythe National Institute of Health Research Biomedical ResearchCentre at Moorfields Eye Hospital and University College LondonInstitute of Ophthalmology. They also thank Elizabeth Johnsonfrom Tufts University, Boston, Massachusetts, United States, forpermission to use the ‘‘L/Z screener’’ for estimating dietary intakeof lutein and zeaxanthin in this study. They also thank the CRESTData Safety and Monitoring Committee (James Loughman [Chair-person and Vision Scientist], Ailbhe Whyte [Medical Ophthalmol-ogist], Michael Harrison [Research Ethics Committee member],and Frank Leonard [Statistician]) for their support and guidanceduring the Central Retinal Enrichment Supplementation Trialsstudy.

Supported by the European Research Council Grant 281096.

Disclosure: K.O. Akuffo, None; S. Beatty, None; T. Peto, None; J.Stack, None; J. Stringham, None; D. Kelly, None; I. Leung,None; L. Corcoran, None; J.M. Nolan, None

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the impact of supplemental antioxidants on visual function ......meso-zeaxanthin (mz), zeaxanthin...

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